1. Field of the Invention
This invention relates to an imaging apparatus and method, and a communication terminal device and, more particularly, is suitably applied to a case of creating information (hereinafter, referred to as identification information) certifying the validly of an identification target, for example.
2. Description of the Related Art
As identification information, unique body features such as iris, finger prints of fingers or a palm are used, which are difficult to be stolen by the third party.
Recently, a blood vessel formation pattern inside a body has been a focus of attention as one of such unique body features. Then an identification apparatus has been proposed to create the blood vessel formation pattern as identification information by using such a feature that deoxygenization hemoglobin (venous blood) or oxygenization hemoglobin (arterial blood) in blood vessels specifically absorb light (near-infrared light) of a near-infrared light band (for example, refer to Japanese Patent Laid-Open No. 2003-30632).
As an imaging apparatus used in an identification apparatus of this kind, an imaging apparatus 1 shown in FIG. 1 has been proposed.
This imaging apparatus 1 has a laser light source 2 which emits near-infrared light. On a light path of the near-infrared light emitted from the laser light source 2, a first filter 3 for letting light of specified near-infrared light band out of the near-infrared light get through, a second filter 4 for letting light of a near-infrared light band which is absorbed in hemoglobin in blood vessels, out of the light which passed through the first filter 3, and an imaging element 5 are arranged in order.
In this case, in a situation where, for example, a human finger FG is inserted between the first filter 3 and the second filter 4, the imaging apparatus 1 emits near-infrared light from the light source 2 to irradiate the finger FG with this via the first filter 3. Since this near-infrared light is specifically absorbed in the intrinsic hemoglobin inside the blood vessel tissues in the finger FG, near-infrared light which passed through the finger FG is entered in the imaging element 5 through the second filter 4 as blood vessel pattern light representing the formation pattern of the blood vessel tissues.
Then the imaging element 5 performs photoelectric conversion on the blood vessel pattern light with a plurality of photoelectric conversion elements which is arranged in a reticular pattern in correspondence with pixels, to create a blood vessel image signal, and sends this to an information creation unit 6. The information creation unit 6 creates identification information based on the blood vessel image signal and outputs this to the outside.
In addition, this imaging apparatus 1 is provided with a shielding unit 7 for shielding light (outside light) in the air coming to the finger FG, thereby eliminating influences of the outside light on the near-infrared light emitted from the light source 2. Therefore, the imaging apparatus 1 is capable of creating a blood vessel image signal in which the blood vessel tissues inside the finger FG are faithfully reflected.
By the way, such the imaging apparatus 1 has a large-scale problem because, to create a blood vessel image signal in which blood vessel tissues are faithfully reflected, the physical shielding unit 7 should be provided to eliminate influences of the outside light on near-infrared light emitted from the light source 2, the physical shielding unit 7 covering not only all units 2 to 5 on the light path of the near-infrared light emitted from the light source 2 but also the finger FG.
In addition, to install the blood vessel imaging function of the imaging apparatus 1 in a communication terminal device such as a portable telephone or a Personal Digital Assistant (PDA) to determine based on identification information which is obtained from the imaging apparatus 1 in communicating with the outside, whether the communication terminal device is being used by the third party, the communication terminal device is hard to be put into practical use due to the shielding unit 7.